invoke set property

procedure TForm2.GetProperty(dispobj: IDispatch; PropertyName: WideString;
                                var retvalue: Variant; Sender: TObject);  
var hr: HRESULT;  
    DispId: integer;  
    value: Variant;  
    params: TDispParams;  
begin  
  hr:=dispobj.GetIDsOfNames(GUID_NULL,@PropertyName, 1, LOCALE_SYSTEM_DEFAULT, @DispId);  
  Label1.Caption:=inttostr(DispId);  
  hr:=dispobj.Invoke(DispId,GUID_NULL,LOCALE_SYSTEM_DEFAULT,DISPATCH_PROPERTYGET,
                  Params,@Value,nil,nil);  
  Retvalue:=Value;  
  Label2.Caption:=inttostr(value);  
end;  

procedure TForm2.SetProperty(dispobj: IDispatch; PropertyName: WideString; Value: OLEVariant; Sender: TObject);  
var   
    hr: HRESULT;  
    DispId: integer;  
    params: TDispParams;  
begin  
   hr:=dispobj.GetIDsOfNames(GUID_NULL,@PropertyName,1, LOCALE_SYSTEM_DEFAULT, @DispId);  
  Label1.Caption:=inttostr(DispId);  
  params.rgvarg:=@Value;  
  params.rgdispidNamedArgs:=@DispIDArgs;  
  params.cArgs:=1;  
  params.cNamedArgs:=1;  
  hr:=dispobj.Invoke(DispId,GUID_NULL,LOCALE_SYSTEM_DEFAULT,                  DISPATCH_PROPERTYPUT,Params,nil,nil,nil);  
 end;

They work fine with Color and Style properties of IGraphAxes:

GetProperty(Graph1.GraphAxes, 'Color', retvalue, Sender);

Or

SetProperty(Graph1.GraphAxes, 'Color',value,Sender);